Steam Power – Calculating Steam Power Output


Calculating steam power output in a steam turbine generator depends on many factors.  The size of the turbine is a factor, the type of steam turbine, the inlet steam pressure and temperature, the exhaust steam pressure and temperature, and the steam flow rate.

Steam power accounts for nearly 90% of the electricity generated in the United States, mostly from nuclear power, coal power, and burning natural gas.  To a much smaller extent, concentrated solar turbines use steam power to generate electricity.

The Rankine cycle uses theories and equations that can help ups determine the steam power output of a steam turbine.

In general, the Rankine cycle is a process that converts heat into work, with the heat being supplied by an external force into a closed system that usually uses water.

Most steam power generators will use this sort of closed cycle system with the external heat source being either nuclear power, fossil fuels, or solar heating power.

The Rankine cycle can help us calculate steam power output of a steam turbine generator using the steady flow form of the first law of thermodynamics for an isentropic turbine:

q = 0 = h2-h1+wt  (Btu/lbm | kJ/Kg)

In this equation the differences between the kinetic and potential energy differences between the inlet and outlet are negligible.  So, from there the equation that will show the steam power turbine work per unit mass passing through the turbine is the difference between the entrance enthalpy and the lower exit enthalpy:

Wt = h1 – h2    (Btu/lbm | kJ/Kg)